Polyamides, silk, and wool fibers are subject to staining by a variety of agents, particularly acid dyes such as FD&C Red Dye No. 40, commonly found in soft drinks. Various stain resist agents have been used, including sulfonated phenol formaldehyde condensates and polycarboxylic acids such as those derived from methacrylic acid or maleic acid. Usually the stain resist agents are applied from an aqueous medium under conditions of controlled pH.
Additionally, polyamide, silk, and wool fibers are subject to soiling. Several of the currently used soil resist agents for nylon carpets are based on polymers derived from perfluoroalkylethyl alcohols. Typically the perfluoroalkylethyl alcohol derivatives are incorporated into acrylic or urethane polymers for application by foam, padding or spraying to various substrates.
Fluorochemical soil resist agents offer little protection from stains caused by acid dyes. Since the fluorochemical soil resist agents do not exhaust from aqueous solutions, they are usually applied in a separate operation from stain resists. Coapplication of the stain resist and soil resist would be more economical. Jones Jr. in U.S. Pat. No. 5,520,962 uses compatible soil/stain resists in a single bath. However, coapplication of conventional stain resists and soil resists often does not provide the desired properties. Additionally, coapplication techniques are not appropriate to all combinations of stain resists and fluorochemicals, especially when the two materials are incompatible or when one chemical impedes the exhaust efficiency of the other.
The incompatibilities result in such problems as phase separation and precipitation in the bath, increased bath viscosity, reduced wetting, excessive foaming, or other unacceptable physical changes which make the stain resist and/or the fluorochemical soil resist not perform on the carpet. Causes for these problems include incompatibilities in pH, concentration, mixed charges (e.g., anionic and cationic components), salt concentration, temperature, or other factors. For applications by exhaustion there may be competition between the soil resist and stain resist exhaust rates onto the fiber.
The nature of the competition between the fluorochemical and stain resist exhaust rates onto the fiber is not well understood. However, it is known that the single step or coapplication of compatible stain resists and fluorochemical soil resists typically encounters conflicting process requirements for optimum and efficient application for one chemical treatment or the other. Although both the stain resist and fluorochemical can be deposited onto the carpet, their final performance is not as good as when separate applications are employed.
Various processes for the separate application of stain and soil resists to carpets have been attempted. Typically a stain resist is applied followed by several finishing steps. This is then followed with a separate application of the fluorochemical soil resist followed by finishing steps. Attempts to apply both the stain resist and soil resist under stain resist conditions have resulted in poor performance due to the competition between the fluorochemical and stain resist exhaust rates onto the fiber. Attempts to apply both the stain and soil resist under the soil resist application conditions have also resulted in various product deficiencies.
It is desirable to have a process in which both the agents conferring soil and stain resistance can be applied whether or not the agents are mutually compatible, and for the finished product to display optimum performance for both treatments. The present invention describes such a process that allows both soil and stain resists to be applied in tandem with a single finishing step.